Patent Literature 1 describes a device, as an electronic device such as a mobile phone, that transmits air-conducted sound and bone-conducted sound to a user. Patent Literature 1 also describes that the air-conducted sound is sound transmitted to the auditory nerve of the user in such a manner that vibration of air caused by vibration of an object is transmitted to an eardrum through an ear canal to vibrate the eardrum. In addition, Patent Literature 1 describes that the bone-conducted sound (vibration sound) is sound transmitted to the auditory nerve of the user via part of a user's body (e.g., external ear cartilage) in contact with a vibrating object.
Patent Literature 2 describes a speaker known as one that transmits sound to a human body by vibration sound. The speaker transmits the vibration generated by a piezoelectric element arranged in a case to a user via a contact for transmitting vibration energy and via a contact pad that is attached to the case and comes in contact with, for example, cartilage around a user's ear.